Polishing cement

Just what you guys want...another wall question. Here goes: I've got 8" block walls inside my basement in front of the original poured-concrete type walls (home built 1911). There is approx. 2-3 inches between the 2 walls with the blocks being plumb. What type of insulation would the readers reccomend? Could go with 2X4 walls, filled with R-11 fiberglass or go with the polysterene sheet. Since I've insulated the floor joist/rim space, the basement has been much warmer (fewer/no drafts). In fact, the basement is downright comfy. I live in central Minnesota. 1. Do I even need to be concerned with insulating the walls? If not, suppose I could go with furring strips on walls. 2. Fiber/sheet reccomendations? 3. Who out there has tapped into a main sewer line in their basement? What type of connection do you use for the cast-iron splice that is BELOW the finished floor?

Just finishing up framing in the walls of my basement finishing project. I have rough openings for 6 doors, and one egress window in the basement. What should be my next step after the walls are finished? I plan on doing a drywalled ceiling. Here's the questions I have: Should I frame around my ducts/pipes next? If so, what should I use? 2x4? 2x2? Do I build the frames on the floor and then attach to ceiling? What is the standard/best practice? Thanks for any info, Mayo